In general, air conditioners include a heater, a cooler and an air purifier. Air conditioners are installed in a room and can establish an agreeable indoor environment by cooling or warming a room.
Air conditioners may perform a cooling operation or a heating operation by controlling the operation of a compressor according to the magnitude of an alternating voltage applied thereto, the temperature inside a room and a desired cooling/heating temperature. Here, the alternating voltage may be a three-phase alternating voltage having three phases: R, S and T phases.
Air conditioners may also include a reverse-phase detection circuit which performs reverse-phase detection on a three-phase alternating voltage and can thus prevent an air conditioner from malfunctioning due to a reverse phase of a three-phase alternating voltage.
However, in order to perform reverse-phase detection, conventional air conditioners need to extract the patterns of all three phases of an input alternating voltage and to compare the phases of the input alternating voltage. Thus, it takes time for conventional air conditioners to perform reverse-phase detection. Therefore, it is difficult for conventional air conditioners to perform reverse-phase detection on an input alternating voltage in real time.